HartsfieldâJackson Atlanta International Airport has been the world's busiest airport every year since 2000; with all airports combined London has the world's busiest city airport system by passenger count.
Tension or Temperature. Dogs may shake as a way of relieving tension. If a dog is feeling nervous or uncomfortable in a situation, it might shake the whole body as a way of shaking out tension. This behavior also may function as a means of getting attention from other dogs or people.
It certainly isn't always the case that a dog is fearful, cold or even excited about something. In more serious cases, shaking could be the sign of illness, including Distemper. But for a dog who seems to shake at random times and has done so from an early age it is much more likely to be 'something they just do'. You must forgive me for my frustration at not being able to get to the scientific bottom of answering the question of why do dogs shake.